The invention relates to improvements in apparatus for transporting discrete commodities, particularly for transporting stacks consisting of paper sheets or the like. More particularly, the invention relates to improvements in apparatus for intermittent transport of one or more files of spaced-apart stacks or piles of superimposed sheets or the like. Still more particularly, the invention relates to improvements in apparatus of the type wherein each file of stacks is transported by several endless conveyors in the form of belts, e.g., by three endless belts which are disposed in parallel vertical planes and are provided with entraining elements in the form of projections or lobes serving to advance as well as to locate the stacks during transport along a predetermined path.
The aforementioned commonly owned copending application Ser. No. 343,742 discloses a transporting apparatus wherein three transporting units are disposed side by side, and each such unit comprises three belts including a centrally located belt whose projections engage the front edge faces of the stacks and two outer belts whose projections engage the rear edge faces of the stacks on or above the respective transporting unit. The belts are trained around pairs of pulleys, and the drive means for the belts comprises a first shaft which transmits torque to the pulleys for the outer belts in each transporting unit and a second shaft which transmits torque to the pulleys for the centrally located belt in each unit. The two shafts receive motion from a common stepping motor.
The apparatus of the aforementioned commonly owned copending application Ser. No. 343,742 operates quite satisfactorily as soon as a stack of paper sheets is properly located between a (leading) projection of the centrally located belt and the (trailing) projections of the outer belts forming part of a transporting unit. However, problems can arise in connection with the delivery of stacks onto the transporting units because the distance between the projections of the centrally located belt and the projections of the outer belts in each transporting unit is fixed. Therefore, it is necessary to urge the leading edge face of a freshly delivered stack against a projection of the centrally located belt while the corresponding projections of the outer belts advance from a lower level to a higher level in order to engage the trailing edge face of such freshly delivered stack. Similar problems can be encountered during removal of stacks from the path which is defined by the transporting apparatus, e.g., from the upper surface of a platform which is installed at a level above the upper reaches of the belts in each of the transporting units. As a rule, it is necessary to accelerate the stacks once the leading projections (on the respective centrally located belts) descend below the associated platforms in order to make sure that the corresponding trailing projections will have room to descend to a level below the platform during movement around the pulleys at the downstream ends of the respective transporting units. If the aforedescribed precautionary measures are not fulfilled, e.g., if the leading edge face of a stack is not urged against the projection of the centrally located belt in the respective transporting unit, the oncoming projections of the outer belts are likely to lift the rear portion of the stack with attendant shifting of sheets in the stack relative to one another. Furthermore, the rising trailing projections which are to engage the trailing edge face of a freshly delivered stack are likely to score or to otherwise deface the sheets of the stack. The trailing projections are also likely to shift the sheets of a stack at the discharge end of the respective transporting unit if the stack is not accelerated before the projections which engage its trailing edge face during transport toward the discharge end of the transporting unit begin to descend to a level below the platform without contacting the trailing edge face of the stack.